Photochromic polyacetylenes responsive to radiation exposure have been disclosed in several U.S. Patents, namely U.S. Pat. Nos. 4,066,676; 4,581,315; 3,501,302; 3,501,297; 3,501,303; 3,501,308; 3,772,028; 3,844,791, 3,954,816, 5,232,820, 5,731,112, 6,017,390, 6,177,578, and 7,445,880. The relevant disclosures in these patents are hereby incorporated by reference.
Radiochromic film is based on the polymerization of diacetylene monomers upon exposure to ionizing radiation (e.g., X-ray). Such polymerization is a combination of intrinsic sensitivity and amount of the adsorbed energy. One of the ways to improve sensitivity as demanded for applications in radiology and radiograph is to dope the active with materials of high atomic (Z) element.
The high Z element adsorbs more kilo-voltage x-ray and generates photoelectrons which in turn increases the energy adsorption by diacetylene monomer to initiate the polymerization. This results in an apparent improvement in the sensitivity of the radiation sensitive materials.
Conventional methods of incorporating a high Z element into the radiation sensitive film typically involve the use of water soluble compounds like CsBr as additives in the coating fluids. The water insolubility of most compounds containing high Z elements has prevented its application in this field since the opaque particles negatively impact the clarity of the film and image quality, and thus cancel out any possible gain from the increased x-ray adsorption. Nanoparticles, having excellent optical properties that can produce a clear film, when well dispersed in media and matrix, can be an excellent alternative to the water soluble additives.
The current invention describes materials, methods and processes to make and apply nanoparticle dispersion into a radiation sensitive film to enhance the radiation sensitivity of self-developing films.